1. Field of the Invention
The present invention relates in general to a production system and method for product assembly, and more particularly to an order assembly production system and method.
2. Description of the Related Art
Conventional production systems can be roughly classified into the following two systems.
One of them is a made-to-stock production system (also called a sale-to-stock production system) in which procedures up to final assembly or shipment are performed based on demand forecast before an order is received, products are stocked, and an actual order is received. The other system is a made-to-order production system (also called an engineering-to-order system) in which a parts design or a product design is started after an order from a customer is received.
In the made-to-stock production system, lead time from order entry to shipment is short. However, since production is advanced based on the demand forecast for each predetermined period (generally, monthly demand forecast), there is a high probability that a balance between demand and supply is lost. Accordingly, when the forecast is failed (the demanded quantity is less than the forecasted quantity), the quantity of stock may be increased due to overproduction. The increase in stock causes obsolete product inventory, product price break, part valuation loss, deterioration in cash flow, or an increase in depreciation. When the demanded quantity is higher than the forecasted quantity, the product is out of stock, so that a sales opportunity thereof may be missed.
Currently, the life cycle of a product becomes shorter in association with a rapid technical innovation. Accordingly, the price of each of the product and the parts sharply comes down. Since market competition heats up, product price competition remarkably heats up. Moreover, user's needs are varied. In order to respond to the variable needs, the number of specifications and the number of product models have to be increased. An electronic device such as a personal computer is one example of the products.
Under the situations, according to the made-to-order production system, production is not made based on demand forecast. Accordingly, the quantity of stock is not increased due to overproduction. However, lead time from order entry to shipment is long. While the product is out of stock in shops for the lead time, a sales opportunity thereof may be missed.
As an example of the conventional individual order production system, “Manufacturing System and Assembly System of Computer System in Order Manufacturing Environment” is described in Japanese Patent Publication (KOKAI) No. 11-285936 (published on Oct. 19, 1988). In this prior-art example, a kit tray is prepared in response to a received order, and the constituent components for respective ordered products are held in the kit tray. The kit tray is transferred to an operation cell, and a team assembles the product in the cell. Thereafter, the product is tested and repaired based on information about an arbitrary problem given to the managing operation cell.
In recent years, manufacturing industries have to efficiently produce various models by a small quantity. In response to various needs of the customers, the following is under review in the made-to-order production system. That is, custom-made models to be manufactured based on specifications desired by the customers are prepared in addition to base models according to specifications determined by manufacturers. For example, as to personal computers, in case of the same model, a memory capacity, an HDD capacity, an optical disk drive, a communicating function and the like can be selected.
However, when all of the combinations of selectable units are set as custom-made model targets, the number of models (model numbers) reaches hundreds to thousands. In a manufacturing department, when a product is manufactured, a manufacturing parts list as a list of parts including a screw that constitute the product is needed every factory model number. The manufacturing parts list is formed by hand. Actually, it is impossible to form the manufacturing parts lists corresponding to thousands of model numbers. Accordingly, the number of custom-made models is limited. Further, a manufacturing line is operated in a model number unit. Accordingly, in diversified small-quantity production of a custom-made model or the like, the number of custom-made models is limited from the viewpoints of the occurrence of losses caused by frequent tooling changes and wasted manual motions.
A production schedule (parts acquisition schedule) for the custom-made model cannot previously be formed. After a customer or a salesperson requests a product, the production schedule is formed. Accordingly, exact delivery time cannot be answered.
Further, a planning or marketing department attempts to control the production of the custom-made model for each model number. However, all of the thousands of model numbers cannot be grasped. When the salesperson sells a product to the customer, he or she does not know which model should be recommended to the customer.
As mentioned above, in the conventional made-to-order production system, in order to stand prepared to manufacture products in accordance with all of specifications that may be requested by the customer, it is necessary to control huge numbers of models. Consequently, there is a problem that it takes very long time for preparation before manufacture (formation of the manufacturing parts list).
For the custom-made model produced by the made-to-order production system, the production schedule therefor cannot previously be formed. Consequently, there is a problem that delivery time is not found exactly.